[CIG-SHORT] Slippery Nodes in Pylith

[Charles Williams]

Hi Nick,

I figured it might be difficult with no friction.  I would think that a very low coefficient of friction would represent a very mature fault that sustains less shear stress than a younger fault.

Cheers,
Charles


> On 17/03/2017, at 3:22 PM, Nick Wogan <nicholaswogan at gmail.com> wrote:
> 
> Charles,
> 
> I couldn't get the SNES solver to converge with friction and cohesion both zero. It converged after ~100 SNES iterations for a coefficient of friction of 0.1 for the particular problem I am looking at.
> 
> The slippery fault is suppose to represent a fault that has had many years to evolve and almost completely relax the shear stress on the fault plane. I suppose 0.1 coefficient of friction is representative of this?
> 
> Thanks,
> Nick
> 
> 
> 
> On Thu, Mar 16, 2017 at 6:24 PM, Charles Williams <willic3 at gmail.com <mailto:willic3 at gmail.com>> wrote:
> Hi Nick,
> 
> It’s only linear if you already know the slip direction.  In the more general case, it’s a nonlinear problem.  Also, I suspect your solution will be unstable if the friction and cohesion are both zero (I might be wrong — you can experiment).  You might need just a bit of friction and/or cohesion.  What is the slippery fault meant to represent?
> 
> Cheers,
> Charles
> 
> 
>> On 17/03/2017, at 1:42 PM, Nick Wogan <nicholaswogan at gmail.com <mailto:nicholaswogan at gmail.com>> wrote:
>> 
>> Brad,
>> 
>> Is this the best way to do slippery faults? I thought slippery faults could be solved linearly. 
>> 
>> [pylithapp.timedependent.interfaces.fault]
>> friction = pylith.friction.StaticFriction
>> friction.db_properties.values = [friction-coefficient,cohesion]
>> friction.db_properties.data = [0.0,0.0*Pa]
>> 
>> What am i missing?
>> Nick
>> 
>> On Thu, Mar 16, 2017 at 4:32 PM, Brad Aagaard <baagaard at usgs.gov <mailto:baagaard at usgs.gov>> wrote:
>> On 03/16/2017 04:29 PM, Nick Wogan wrote:
>> Hi,
>> 
>> Is there a slippery nodes option for faults available?
>> 
>> Thanks,
>> Nick
>> 
>> See Section 6.4.5 Dynamic Earthquake Rupture in the PyLith v2.1.4 manual.
>> 
>> Regards,
>> Brad
>> 
>> 
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> Charles Williams I Geodynamic Modeler
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Charles Williams I Geodynamic Modeler
GNS Science I Te Pῡ Ao
1 Fairway Drive, Avalon 5010, PO Box 30368, Lower Hutt 5040, New Zealand
Ph 0064-4-570-4566 I Mob 0064-22-350-7326 I Fax 0064-4-570-4600
http://www.gns.cri.nz/ <http://www.gns.cri.nz/> I Email: C.Williams at gns.cri.nz <mailto:your.email at gns.cri.nz>
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